Anaemia, iron deficiency - Causes of iron deficiency anaemia

Iron deficiency anaemia occurs when the body doesn't have enough iron, leading to the decreased production of red blood cells. Red blood cells carry oxygen around the body.

A lack of iron can be caused by several factors. Some of the most common causes of iron deficiency anaemia are outlined below.

Monthly periods

In women of reproductive age, periods are the most common cause of iron deficiency anaemia.

Usually, only women with heavy periods develop iron deficiency anaemia. If you have heavy bleeding over several consecutive menstrual cycles, it's known as menorrhagia.


It's also very common for women to develop iron deficiency during pregnancy.

This is because your body needs extra iron to ensure your baby has a sufficient blood supply and receives necessary oxygen and nutrients.

Some pregnant women require an iron supplement, while others may need to increase the amount of iron in their diet.

Read more about vitamins and nutrition in pregnancy.

Gastrointestinal blood loss

The gastrointestinal tract is the part of the body responsible for digesting food. It contains the stomach and intestines.

Bleeding in the gastrointestinal tract is the most common cause of iron deficiency anaemia in men, as well as women who've experienced the menopause (when monthly periods stop).

Most people with gastrointestinal bleeding don't notice any obvious blood in their stools and don't experience any changes in their bowel habits.

Some causes of gastrointestinal bleeding are described below.

Non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause bleeding in the stomach. Ibuprofen and aspirin are two commonly prescribed NSAIDs.

If your GP thinks your medication is causing gastrointestinal bleeding, they can prescribe a less harmful medicine. However, don't stop taking a medicine you've been prescribed unless your GP advises you to.

Stomach ulcers

The acid in your stomach, which helps your body digest food, can sometimes eat into your stomach lining. When this happens, the acid forms an open sore (an ulcer). This is also known as a stomach ulcer or a peptic ulcer.

Stomach ulcers can cause the stomach lining to bleed, which can lead to anaemia. In some cases, the bleeding can cause you to vomit blood or pass blood in your stools. However, if the ulcer bleeds slowly, you may not have any symptoms.

Gastrointestinal cancer

In a few cases, gastrointestinal bleeding can be caused by cancer, usually stomach cancer or bowel cancer.

When trying to establish the cause of anaemia, your GP will check for possible signs of cancer.

If your GP suspects cancer, you'll be referred to a gastroenterologist (a specialist in treating digestive conditions) for a more thorough examination. This means that if cancer is found, it can be treated as quickly as possible.

If you're 60 years old or over and have iron deficiency anaemia, your GP should refer you to a specialist to rule out bowel cancer. Your appointment with the specialist should be within two weeks of your GP referring you.


Gastrointestinal bleeding can also be caused by a condition called angiodysplasia. This is the result of abnormal, fragile superficial blood vessels in the gastrointestinal tract, which can cause bleeding.

Chronic kidney disease

People with chronic kidney disease (CKD) often develop iron deficiency anaemia.

Most people with CKD who have iron deficiency anaemia will be given iron supplement injections, although daily tablets may be tried first.

You can read more about treating anaemia in people with CKD on the National Institute for Health and Care Excellence (NICE) website.

Other causes

Other conditions or actions that cause blood loss and may lead to iron deficiency anaemia include:

  • inflammatory bowel disease ‐ a condition that causes redness and swelling (inflammation) in the digestive system, such as Crohn's disease and ulcerative colitis
  • oesophagitis ‐ inflammation of the gullet (oesophagus) caused by stomach acid leaking through it
  • schistosomiasis ‐ an infection caused by parasites, mainly found in sub-Saharan Africa
  • blood donation ‐ donating a large amount of blood may lead to anaemia
  • trauma ‐ a serious accident, such as a car crash, may cause you to lose a large amount of blood
  • nosebleeds ‐ having regular nosebleeds may lead to anaemia, although this is rare
  • haematuria (blood in your urine) ‐ but this rarely causes anaemia and may be a symptom of another condition


Malabsorption is when your body can't absorb iron from food, and is another possible cause of iron deficiency anaemia.

This may happen if you have coeliac disease, a common digestive condition where a person has an adverse reaction to gluten, or surgery to remove all or part of your stomach (gastrectomy).

Lack of iron in your diet

Unless you're pregnant, it's rare for iron deficiency anaemia to be caused solely by a lack of iron in your diet.

However, a lack of dietary iron can increase your risk of developing anaemia if you also have any of the conditions mentioned above.

Some studies suggest vegetarians or vegans are more at risk of iron deficiency anaemia because of the lack of meat in their diet.

If you are vegetarian or vegan, it is possible to gain enough iron by eating other types of food, such as:

  • beans
  • nuts
  • dried fruit, such as dried apricots
  • wholegrains, such as brown rice
  • fortified breakfast cereals
  • soybean flour
  • most dark-green leafy vegetables, such as watercress and curly kale

If you're pregnant, you may need to increase the amount of iron-rich food you consume during pregnancy to help prevent iron deficiency anaemia.

Read more about vegetarian and vegan diets and good sources of iron.


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